The invention relates to the field of additive manufacturing methods and prototyping or rapid prototyping.
Methods for additive manufacturing differ from subtractive methods such as milling, drilling and erosion in that material is combined into a component. To this end, the material has to be in a state in which it does not in itself define a shape, but rather can be brought into a shape. Starting materials such as workable masses, pastes, powders, liquids etc. meet this requirement. While it is intuitively understood that workable masses and pastes can be shaped into a structure, with powders and liquids this is not directly the case. Normally, the particles of a powder are linked together using an auxiliary substance, for example a binder. Fluids, such as flowable particle suspensions, for example, can be formed into a structure by drying or by a phase transition from liquid to solid. One class of earlier methods for additive manufacturing is constituted by powder-based methods, in which particles of powder are built up in layers, typically 50 to 200 μm thick, and are connected together in each of these layers by the local application of a binder or by local melting with a laser beam. The binder-based powder methods were developed at the Massachusetts Institute of Technology in Cambridge, USA, and the laser-based methods were developed at the University of Texas in Austin, USA in the early 1980s/early 1990s and are known as 3 D printing or selective laser sintering. Both methods are now well established among the (now many) additive manufacturing methods, and with regard to the number of manufactured components, they clearly count among the leading current methods. In addition to a continual optimization of the technologies underlying these two methods, in the 30 years since their invention, there have substantially been no further developments in 3 D printing or selective laser sintering.
In additive manufacturing methods, which are based on building up powdered starting material layer-by-layer, stabilization of the structures (components) embedded in the powder bed is problematic. A fundamental problem in powder-based methods is and always has been the fact that the powder bed, i.e. all of the powdered material which is piled up when building up the layers but which has not been bound into the component, does not support the embedded structure (component) sufficiently during the construction process. When applying a new layer of powder, the already consolidated structure in the powder bed can be displaced, which results in defects in the structure or even in complete loss of structure. For this reason, in powder-based manufacturing technologies, in addition to the component to be manufactured using the appropriate manufacturing technology, additional so-called support structures are also constructed. These support structures anchor the component to be constructed with the working platform and thus fix it into the coordinate system of the building-up chamber of the facility.
Furthermore, support structures are needed when particularly complex geometries are to be produced. Removing the support structures after the actual additive manufacturing process requires an additional process step which is time-consuming and does not lend itself to automation, and thus runs counter to the remit of autonomous manufacturing which can be carried out by additive manufacturing. Thus, there is a need for stabilizing the powder bed in a manner such that support structures can be completely dispensed with, which does not affect the manufacturing process itself and, more importantly, which does not hinder removal of the component from the powder bed. A powder bed with aggregated particles would, for example, hinder ready removal of the component from the powder bed. In particular, removal of the powder which did not belong to the component at locations on the component which were difficult to access would be problematic. The final point is also highly problematic when removing the support structures and constitutes distinct constraints when designing components for powder-based additive manufacturing.
After the building-up process, the support structure has to be separated from the actual component. This process is time-consuming and very difficult to automate.